Dispenser systems that apply two-component polyurethane-based adhesives made up “resin” and “hardener” reactive component fluids are known. Conventionally, the component fluids are pumped from supply reservoirs, barrels or other containers to a dispensing head. The component fluids are then combined within a disposable application tip such as a static mixer tip. The reactive component fluids combine into an adhesive that is applied to work surfaces.
Construction projects necessitate adhesives to be applied to work surfaces in specific forms to achieve a desired degree of adhesion between the work surface and an applied material. For example, adhesive-applied roofing components may require a degree of adhesion corresponding to specific “wind uplift resistance” requirements. To meet wind uplift resistance requirements, adhesives may be applied in a high-pressure spray form or a low-pressure bead form.
Conventional high-pressure spray adhesive systems dispense adhesives at a high pressure of approximately 1000 psi in the form of atomized, fine droplets. While spray application allows for a reasonably uniform adhesives application on work surfaces to meet higher wind uplift resistance ratings, there are drawbacks. High-pressure sprays require high-pressure pumping systems to operate. These pumping systems contain high-pressure proportioning pumps that are expensive as well as difficult to maintain and operate.
Additionally, the end application of adhesives through a spray system is difficult to control. Atomized droplets can disperse and land away from target work surfaces, contaminating other undesired areas with adhesive. This necessitates the installation of protective barriers before application or clean up expense afterward. Also, spray system operators must wear special respiratory equipment to prevent inhalation of atomized droplets.
Conventional bead adhesive systems dispense adhesives at a lower pressure in the range of approximately 150 to 400 psi in a continuous single bead or stream. The bead is applied to the work surface at repeating intervals as required by a project, such as at 4, 6 or 12 inch on-center intervals along a work surface. A drawback of bead adhesive systems is that they do not provide a uniform layer of adhesive across the surface area of work surfaces. That is, bead adhesive systems provide non-uniform adhesive application to work surfaces. Bead adhesive systems are used for projects having lower adhesion or wind uplift resistance requirements than high-pressure spray applications.
Additionally, mixed component fluids can harden within the dispensing head and application tip passages after use, creating difficult to clear blockages.